despite accomplishing the same basic goal, theyre really not very similar

pyside/pyside2 are just python QT4/QT5 bindings wrapping the C++ api.
very similar to pyqt, and basically any other LANGUAGE-GOES-HERE wrapper around GUI-LIBRARY-GOES-HERE

pyotherside is a QML plugin to expose a python interpreter. its a much weirder, much simpler concept